USSR: What tuned me into it was the wasp-shaped cartridges that were being produced using my carbide die set. That has pretty much gone away with the change to steel dies. Can't say if all steel .45 Colt sizing dies have the built-in taper, but the RCBS steel dies seem to.
Like AMP, I've lingered in "blissful ignorance" for 50+ years! But here's a question...do you lube your brass as is universally recommended, prior to sizing with the steel dies? For the shorter ones, .32 Long, .30 Luger etc., I've never bothered and have never stuck a case. Just wondering here in print vs. going down to the shop and digging out a 1960 vintage set of steel Lyman .45 Colt dies if they're still there and not hopelessly rusted up.
Wonder too, if the neck thickness would make up for the difference in sizing die diameters. .45 ACP having thicker necks than .45 Colt, or am I remembering .45 Colt brass from 30-40 years ago? Eye-balling it, it appears to be thicker.
At most, and even with carbide dies, I've found that a VERY Light wiff of spray-on lube seems to help with some that shouldn't need it...9mm Luger in Redding dies comes to mind.
But with some of the old 310 Tong tool sizers, I had to lube every case, regardless of caliber, and carefully allowing me to open the pliers type handles without inducing a hernia. Why I bothered to do that with a perfectly usable set of presses, dies, and bench tools down stairs is open to discussion but I've found it to be satisfying to sometimes harken back to a simpler time...see how the really old timers did it, and then to savor the results that are every bit as good.
Just some musing here...YMMv Rod